1. Field of the Invention
The present invention relates generally to methods and apparatus for imprinting images on the surfaces of three-dimensional objects. More particularly, the invention concerns a novel, improved method and apparatus for non-contact, high-quality, distortion-free printing of images on non-planar surfaces of three-dimensional objects using ink jet printing technology.
2. Discussion of the Prior Art
Various types of image transfer techniques have been suggested in the past for imprinting images on a number of different material surfaces including cloth, wood, metal and ceramics. A very common technique, which has been widely used, is silk screening. However, such a technique is generally limited to printing on smooth, flat surfaces. Further, such technique produces a relatively low quality prints when compared to that produced by lithography, gravure, letterpress sublimation and laser printing.
When the image is to be transferred to a metal surface, prior art sublimation techniques are frequently used. For example, Blake et al, U.S. Pat. No. 3,484,342 issued Dec. 16, 1969 and Fromson et al, U.S. Pat. No. 4,201,821 issued May 6, 1980 both suggest decorating unsealed and coated anodized aluminum using sublimation techniques. However, Sublimation processes also have substantial drawbacks, particularly when the surface of the object, which is printed, is non-planar. Transferring an image or graphic to a sphere or curved, cylindrically tapered surface by means of sublimation, is extremely difficult and such an approach, if achievable at all, would typically result in a poor quality, highly distorted image.
When printing on non-planar surfaces is required, several techniques have been suggested. For example, U.S. Pat. No. 4,741,288 issued to Stirbis et al discloses an apparatus for decorating a cylindrical can. The Stirbis et al apparatus makes use of a multiple station ink supply and a transfer apparatus for transferring ink from an ink fountain to a rotatable inking blanket wheel through a plate cylinder. The apparatus includes an ink image registration adjustment apparatus and an axial and circumferential tightness control apparatus operatively associated with each plate cylinder and each ink supply and transfer apparatus. In addition to techniques involving the use of rotatable inking wheels such as described in Stirbis et al, other techniques, which have been suggested for imprinting images on non-planar surfaces, include electrophotographic imaging and magnetic imaging. As a general rule, these techniques have met with limited commercial success.
U.S. Pat. No. 5,831,641 issued to Carlson discloses a method and apparatus for imprinting images on non-planar surfaces, including the surfaces of various types of three-dimensional articles, such as baseball bats. The apparatus includes a modified ink jet plotter coupled with an article positioning apparatus which functions to automatically maintain the surface of the article to be printed within a plane substantially parallel to and slightly spaced apart from the place within which the ink jet nozzles of the ink jet plotter reside.
Another prior art technique, which is frequently used to decorate surfaces, such as anodized aluminum surfaces, involves the use of transfer films. These films typically overlay the metal surface and undesirably, are subject to film deterioration and unattractive abrasion. A very popular prior art printing technique, which has found wide acceptance in recent years, is ink jet printing. Within perhaps the last five years this technology has become the dominant technology for printing color images and graphics in the office and home markets. Ink jet printing basically involves a process whereby ink particles are projected in a continuous stream toward the surface to be imprinted using appropriate computer control to create text and graphics on the printing substrate. A number of different types of ink jet printers/plotters are readily commercially available from sources such as Calcomp, Packard Bell, NEC Technologies and Mutoh America, Inc.
As will be better understood from the discussion which follows, the method and apparatus of the present invention overcomes most of the problems encountered in prior art attempts to print detailed images on non-planar surfaces by employing a uniquely modified prior art ink jet image transfer technique.
It is an object of the present invention to provide a method and apparatus for imprinting high quality images on non-planar surfaces, including the surfaces of various types of three-dimensional articles formed from a number of different types of materials.
Another object of the invention is to provide a method and apparatus of the aforementioned character in which the non-planar surfaces are printed using a uniquely modified ink jet image transfer technique.
Another object of the invention is to provide a method as described in the preceding paragraphs in which the image is printed on the surface of the article using a plurality of ink jet cartridges, the nozzles of which never touch the surface of the article, which is being printed.
Another object of the invention is to provide an apparatus of the character described in the immediately preceding paragraph which includes a novel article positioning apparatus which functions to controllably rotate the article to be printed and to automatically maintain the longitudinal axis of the article within a plane substantially parallel to and spaced apart from the plane within which the ink jet nozzles reside.
A specific object of the invention is to provide a method and apparatus for imprinting detailed color images on the tapered cylindrical surface such as that found on the barrel and intermediate surfaces of a baseball bat.
Another object of the invention is to provide an apparatus of the class described in which the article positioning portion of the apparatus is operably coupled with a conventional type of commercially available ink jet plotter.
Another object of the invention is to provide an apparatus for imprinting high quality images on non-planar surfaces that is simple to use, is reliable in operation and requires minimum maintenance.
By way of brief summary, a major advantage of the method and apparatus of the present invention is the ability to produce high-quality, multi-colored prints on non-planar surfaces of the character not readily adapted to pass through printing machinery, including surfaces found on a number of differently configured, three-dimensional articles such as baseball bats and the like. In this regard, a particular advantage of the apparatus of the present invention is its ability to print high quality images on curved wood and metal surfaces without the dispensing nozzles of the ink jet cartridges of the apparatus coming into physical contact with the surface to be printed.
In one embodiment of the invention, the article holding and positioning apparatus of the invention is coupled with a conventional, mircoprocessor based digital plotter of the character having a plurality of ink jet cartridges which travel longitudinally of the print zone of the plotter. Typically, three ink jet cartridges contain ink of the three primary colors, namely red, yellow and blue. While a fourth cartridge contains black ink. This allows the computer program developed and stored in the computer memory to cause the application of a multiplicity of individual ink dots of various colors to the work surface so that, when combined by the human eye, appear as photo quality images. In operation of the apparatus of the invention, the article to be imprinted is typically rotated relative to the ink jet cartridges and the surface to be imprinted with the longitudinal axis of the article continuously maintained in a plane which is parallel to and spaced apart from the plane within which the ink jet nozzles reside.
In one form of the method of the invention a computer is used to communicate to the printing apparatus information containing the predetermined pattern to be printed which has either been previously scanned or originally generated using specialized software. The pattern information is typically stored in the computer memory and then sent via cable to the printing apparatus which preferably comprises a conventional printer having four color ink jet print heads capable of dispensing pigmented inks or dyes comprised of either a solvent or water base material. A printed circuit board operably associated with the cable controllably fires the nozzles of the print heads to spray microdots of ink onto the surface to be printed in the predetermined pattern.
According to one embodiment of the invention, the microdots have a diameter of approximately 0.0500-mm (0.002 inches) thereby enabling intricate images to be imprinted on the surface. Upon contact with the surface, the ink solidifies and leaves a digitally generated or scanned image or graphic on the surface without the ink jet nozzles ever coming into physical contact with the surface.
Images to be applied to irregular, non-linear surfaces as occur with changing diameters that are rotating at a constant angular rate can be printed to result in linear appearance by computer programming. The subject apparatus can also achieve the linear appearance by producing graphics that compensate dimensionally for the changing diameters and then, by scanning the graphic artwork, computer data can be recorded and stored for use on the subject equipment when desired.
Computer stored images can be edited on the computer monitor screen to eliminate images, add images or erase spaces for insertion of images. Such images can be nomenclature; video camera generated photo quality images (people, objects, animals, etc.). Changes can be accomplished expeditiously just prior to printing.
Using the techniques described in the preceding paragraphs, high quality images can quickly and easily be imprinted on a variety of different types of materials and upon the non-planar surfaces of a number of types of irregularly configured three-dimensional articles.